High current bushing



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ATTORNEY Nov. 1, 1938. 'r. F. BRANDT HIGH CURRENT BUSHING Filed OGt. 12, 1935 Patented Nov. 1, 1938 UNITED STATES PATENT OFFICE HIGH CURRENT BUSHING Thomas F. Brandt, Barberton, ()hio, assignor to The Ohio Brass Company, Mansfield, Ohio, a corporation of New Jersey Application October 12, 1935, Serial 110, 44,761

3 Claims. (cam-31a) This invention relatesto high current electric bushings, and has ior one 01' its objects the provision oi a bushing insulator having a heavy conductor extending entirely through the insulator 5 and having means to compensate for differential expansion and contraction of the conductor relative to the dielectric member, while at the same time maintaining a tight housing within the dielectric member for insulating liquid.

10 A further object of the invention is to provide a fluid tight connection between the conductor and the housing which will permit expansion and contraction of the conductor without danger of leakage.

15 A further object of the invention is to provide lowing specification, and it is more particularly pointed out in the appended claims. 25 In the drawing:

Fig. l is a part elevation and part section showing one embodiment of the present invention.

Fig. 2 is a view similar to Fig. 1 showing a modifled form of the invention. so In the form shown in Fig. 1, the numeral l designates a conductor rod which has a relatively large cross sectional area for very heavy electrical currents. The numeral II designates a metallic flange member which may be secured upon the 33 top ofa transformer tank or other housing for electrical apparatus to which the conductor rod Ill is connected. The rod l 0 is insulated from the flange H by a bushing insulator comprising a sleeve 12 which extends through anopening in 40 the flange and is provided with a shoulder I3 upon which the flange ii is supported. A cone i4 oi insulating material has its lower end supported upon the flange H and carries an expansion chamber l5 uporrits upper end. The mem- 45 hers l2 and i4 may be made of any suitable dielectric material, but porcelain is the material most commonly used for this class of devices. Gaskets l6 and "are provided to insure liquid tight joints between the flange II and the di- 50 electric members. A third gasket i8 is interposed between the upper end of the cone l4 and the expansion chamber l5 to provide a tight joint at this point. An insulated flux control I! is electrically connected with the flange ii and pro- 55 iects upwardly inside the cone H to prevent disconductor rod l0.

charge from the top of the flange. As shown in the drawing, the conductor rod I0 is a plain cylindrical rod threaded at its upper and lower ends to receive terminal members. This provides a continuous conductor passing entirely through 5 the bushing without any interruption or joints to cause heating or resistance in the path of the heavy current. A fitting is threaded on the lower end of the rod and bears upon' the lower end of the bushing sleeve I2, a gasket 2i being 10 provided to insure a tight joint at this point.

Thefltting 20 may be provided with a removable pipe plug at 22 to facilitate draining oi the oil from the interior of the bushing. The various parts of the bushing are held .tightly cornpressed against their gaskets by a series of helical springs 23 spaced about the interior of the expansion chamber l5 and bearing upon the bottom flange of the chamber housing. A plurality of springs spaced about the conductor [0 avoids the heating effect that would be produced by magnetic induction, due to the heavy current in the conductor, 11 a single steel spring were used encircling the conductor. A ring 24 rests upon the upper ends of the springs 23 and supports a 25 flange ring 25 threaded on the upper end of the The springs 23 are held in compression by the ring 25 so that they will insure pressure on the gaskets in the various joints of the bushing. The expansion chamber l5 is'provided with a cover 26 which is placed over the flange ring 25 after the bushing has been assembled and is soldered in place at 21 toinsure a tight joint at this point. A removable pipe plug 28 provides means for filling the bushing with oil after it has been completely assembled.

A ring nut 29 is threaded on the upper end of the conductor rod Ill above the top of the cover plate 26, and is connected to the cover plate by an 0 expansion bellows 30, preferably of thin sheet metal, which insures a tight closure at the top of the expansion chamber. The ring nut 29 is soldered to the upper end of the bellows 30 and the lower end of the bellows is soldered to the cap 26 and the ring 29 is also soldered to the conductor rod ill, after it has been adjusted to the proper position. This insures a tight connection between the expansion chamber and the conductor rod so that all danger of leakage is avoided. The flexible bellows 30 permits expansion and contraction of the conductor rod relative to the bushing without producing any stress upon the dielectric member or other parts of the bushing.

A breather opening 3| is provided in the expansion chamber I! to allow for expansion and contraction of the fluid inside of the bushing. The current passing through the conductor l may be very heavy and it is desirable that no portion of this current be shunted to the springs 23 or the wall of the expansion chamber, as current in these parts might produce undesirable heating sufficient to loosen some 01 the soldered joints. To avoid any such shunting efiect, the inner edge of the lower portion of the expansion chamber I is covered by an insulating ring 32, and a similar insulation is provided at 33 between the ring 24 and the conductor. The voltage between these points, oi. course, is very low so that a slight insulation will be sufilcient. The heavy conductor i0 passing entirely through the bushing without any interruption provides a very low resistance path for heavy currents, so that heating is reduced to a minimum and the springs 23 insure a tight flt at all of the joints between the metal and porcelain parts, and the expansion bellows 30 insures a tight joint at the top of the-expansion chamber so that all danger of leakage is entirely avoided.

The form of the invention shown in Fig. 2 is quite similar to that in Fig. 1 except that in this form the conductor rod 35 does not project at the ends of the bushings but is threaded onto the terminal members which form the ends of the bushing housing. The lower terminal member 36 bears upon the porcelain sleeve 31 and is threaded onto the lower end of the rod 35. The terminal member 36 is provided with a threaded end 38 for connection with the apparatus inside of the housing on which the bushing is mounted. The housing flange 39 and cone 40 are similar to the corresponding members in Fig. 1.

In Fig. 2 the cover cap 4| for the expansion chamber 42 is provided with terminal lugs 43 for cover cap 4! to compress the gaskets at the joints between the parts of the bushing and insure tight fits at these points. 'An expansion bellows 45 connects the expansion chamber 42 and the cover 4| to allow expansion of the conductor rod 35 and maintain a tight joint at the top of the bushing, as well as to provide for relative movement of the parts under the action of the springs 44.

In assembling the bushing shown in Fig. 2, the rod 35 may be screwed into the cover cap 4| and sweat in place by means of solder in the threaded joint. The cover cap is provided with a rib 46 which fits into a notch in the top 01 the lower member 42 so as to prevent relative rotation between the expansion chamber and its cover cap. Rotation of these parts relative to each other would tend to break the soldered joints at the ends of the bellows 45 or between thecover cap and the conductor. After the parts of the expansion chamber and upper end of the conductor are assembled, they are placed on the bushing and the springs 44 compressed by a suitable jig, after which the lower terminal 35 is threaded onto the lower end of the conductor so that when the jig is released,the tension of thesprings 44 will hold the bushing together and, at the same time, produce pressure on the threaded joints at the ends of the conductor rod so as'to insure good electrical connection. 01' course, the solder in the upper Joint also insures electrical connection at this point.

Another method of assembling the bushing is to solder the lower threaded Joint and then while the expansion chamber is held in place by a jig with the springs compressed, the conductor rod is screwed into the opening in the cover cap 4|. This method may also be used where the conductor rod 35 extends integrally through the lower terminal, as is shown in Fig. 1. In this case, it is of more importance to solder the lower joint in order to prevent leakage of oil through the threads of the joint. To facilitate this second method of assembly,- the bushing may be assembled in an inverted position.

I claim:

1. The combination witlra conductor rod, 01' a supporting flange having an opening through which said rod extends, a bushing insulator having separate portions forinsuiating said rod and flange, a metal spring for holding the portions 01' said insulator in close connection, fittings for receiving the stress of said spring, and a spacer of solid dielectric material interposed between said rod and one of said fittings ior insulating said one of said fittings from said conductor rod to prevent shunt currents from passing through said spring.

2. The combination with a conductor rod, of a supporting fiange having an opening through which said rod extends, a bushing insulator having separate parts thereof bearing on opposite sides of said flange, a fitting secured to said rod and having bearing connection with one 01 said parts, an expansion chamber having bearing connection with the other of said parts, a metal spring for exerting pressure on said parts to hold said parts together, a fitting providing connection between said conductor rod and said spring, said fitting comprising a solid dielectric spacer for insulating said spring from said conductor rod, said spring also having bearing connection with said expansion chamber, and means for insulating said expansion chamber from said conductor rod adjacent the bearing connection thereof with said spring.

3. In combination a conductor rod, a supporting flange having an opening through which said rod extends, tubular dielectric members surrounding said rod and bearing on opposite sides of said flange respectively, an expansion reservoir hearing on one of said dielectric members, a cover for said reservoir threaded on one end of said rod, 2. metal spring interposed between said reservoir and its cover, a fitting threaded on the end of said conductor opposite said reservoir and bearing on the other dielectric member, an expansible bellows connecting said reservoir with its cover to form a liquid tight seal therebetween and means formed 01' solid dielectric material interposed between said conductor and said reservoir to prevent shunt currents irom traversing said spring and said bellows.

THOMAS P. BRANDT. 

